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Register a new userCP violation in charged Higgs decays in the MSSM
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In the MSSM with complex parameters loop corrections to the decays $H^+ to t bar{b}$ and $H^- to bar{t} b$ with $t to b W$ and $W to l u$ lead to CP-violating asymmetries: a decay rate asymmetry, a forward-backward asymmetry and an energy asymmetry. We derive explicit formulas for them and perform a detailed numerical analysis. We study the dependence on the parameters and the phases involved. In particular, the influence of the running Yukawa coupling is taken into account. The decay rate asymmetry can go up to 25%, the forward-backward and the energy asymmetry up to 10%.
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We study the effects of CP violation in charged Higgs boson production $ppto t H^pm + X$ at the LHC, as well as in the charged Higgs boson decays $H^pm to t b$ and $H^pm to W^pm H_i^0$, $i=1,2,3$. The study is done in the framework of the type II complex Two Higgs Doublet Model (2HDM) with softly broken $Z_2$ symmetry. In this model violation of CP invariance is induced by the complex parameter $m^2_{12}$ of the tree-level Higgs potential. We calculate the CP violating rate asymmetries for $H^+$ and $H^-$ production and decays as well as for the combined processes at one-loop level and perform a detailed numerical analysis. All calculations are done with the automatic amplitude generator FeynArts and the calculational tool FormCalc, for which we have written a complete complex 2HDM model file and relevant fortran drivers. The implementation of the complex 2HDM in FeynArts and FormCalc is described. In comparison with the analogous results in the MSSM, all considered CP violating asymmetries are smaller by an order of magnitude and do not exceed 2 to 3%.
The MSSM with explicit CP violation is studied through the di-photon decay channel of the lightest neutral Higgs boson. Through the leading one-loop order H1 --> gammar.gamma is affected by a large number of Higgs-sparticle couplings, which could be complex. Our preliminary scan over the Supersymmetric parameter space shows that more than 50% average deviations are possible, in either direction, in the corresponding branching ratio, with respect to the case of the CP-conserving MSSM. In particular, our analysis shows that in the presence of a light stop (with mass ~ 200 GeV) a CP-violating phase Arg(mu) ~ 90(deg) can render the H1 --> gamma.gamma branching ratio more than 10 times larger, for suitable combinations of the other MSSM parameters.
The Minimal Supersymmetric Standard Model (MSSM) with explicit CP violation is studied with the help of the di-photon decay channel of the lightest neutral Higgs boson. Effects of CP violation, entering via the scalar/pseudo-scalar mixing at higher order as well as through the Higgs-sfermion-sfermion couplings at tree-level, are analyzed in the MSSM with and without light sparticles. A light stop may have a strong impact on the decay width and Branching Ratio (BR) of the decay process H_1 -> gamma gamma, whereas other light sparticles have only little influence. In some regions of the MSSM parameter space with large CP-violating phase phi_mu ~ 90 degrees a light stop can change the BR by more than 50%.
Decades of precision measurements have firmly established the Kobayashi-Maskawa phase as the dominant source of the CP violation observed in weak quark decays. However, it is still unclear whether CP violation is explicitly encoded in complex Yukawa matrices or instead stems from spontaneous symmetry breaking with underlying CP-conserving Yukawa and Higgs sectors. Here we study the latter possibility for the case of a generic two-Higgs-doublet model. We find that theoretical constraints limit the ratio $t_beta$ of the vacuum expectation values to the range $0.22 leq t_beta leq 4.5$ and imply the upper bounds $M_{H^pm}leq 435$ GeV, $M_{H_{2}^0} leq 485$ GeV and $M_{H_{3}^0} leq 545$ GeV for the charged and extra neutral Higgs masses. We derive lower bounds on charged-Higgs couplings to bottom quarks which provide a strong motivation to study the non-standard production and decay signatures $p p to qb H^pm(to q^prime b)$ with all flavors $q,q^prime=u,c,t$ in the search for the charged Higgs boson. We further present a few benchmark scenarios with interesting discovery potential in collider analyses.
Precision tests of the Kobayashi-Maskawa model of CP violation are discussed, pointing out possible signatures for other sources of CP violation and for new flavor-changing operators. The current status of the most accurate tests is summarized.
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